This invention relates to a seal and a method of sealing field emission devices and more particularly, to a high vacuum seal in devices with a flat profile.
Flat panel displays incorporating field emission devices require good vacuum conditions for peak performance and long operating lifetimes. The method in which the vacuum seal is made greatly influences the overall vacuum conditions. Because field emission displays have a larger surface area-to-volume ratio than almost any other vacuum product, the task of producing good vacuum is much more difficult than in other vacuum devices.
There are problems with using established methods to make a seal in field emission displays. One prior art sealing method is commonly referred to as the xe2x80x9ctubulator tip-offxe2x80x9d method and is used to seal a completely glass enclosure. In this method, the act of melting the tip-off area of the glass with heat during the tip-off produces a pressure burst that sets the initial vacuum level within the enclosure at 10xe2x88x925 torr or greater. A tubular stump remains on the back of the display, which reduces the flat form factor of the final product.
A second prior art sealing method is commonly referred to as an xe2x80x9cintegral sealxe2x80x9d. The display is generally sealed in one step at high temperature using a frit or other means, and up to 1 torr of gas can be deposited within the display envelope during the sealing process. This gas must be removed with additional gettering including flashable getters and non-evaporable getters. Significant expense is incurred to clean up the vacuum envelope to levels required for field emission.
Thus, there is a need for a sealed vacuum envelope and method of producing the sealed vacuum envelope for a field emission display which has a flat form factor, produces as low a pressure as possible at the seal, and allows for the activation of a getter within the envelope.